The dev stated "Setting the following env variables might fix it? Honestly not sure with this one." but has also closed the issue stating "Web concurrency now defaults to a single worker. I'm unsure if this changes the Unraid template."
Mealie has a known bug that causes an endlessly large backup file.
The dev has stated that he will not address the issue unless someone else provides a PR, as they will not take on the additional burden to support Unraid.
Link to said issue.